Delta DP600 motor replacement

[Nmhuntr]

I have a single phase 3/4hp motor on my old Delta DP600 I am restoring. I would like to use a VFD to control the RPMs on it as opposed to changing belts every time. I do t k one if this is something that will work on my single phase motor. I am looking for a 3/4hp 3 phase but it needs to have a 3/4” shaft and for all of my searching I cannot find one. Does anyone have any suggestions?
Thanks

 

[micromind]

A basic standard 56 frame (a LOT of 3/4HP motors are 56 frame) has a 5/8" shaft. 5/8 to 3/4 bushings are available. A 66 frame motor has a 3/4" shaft but they're fairly rare.

If the motor drives a pulley, just get one the same diameter but with a 5/8" bore. They're very common, even the step type.

A single phase motor like yours will not work on a VFD. VFDs are available that will accept single phase in and make 3Ø out.

 

[Davefr]

I have a single phase 3/4hp motor on my old Delta DP600 I am restoring. I would like to use a VFD to control the RPMs on it as opposed to changing belts every time. I do t k one if this is something that will work on my single phase motor. I am looking for a 3/4hp 3 phase but it needs to have a 3/4” shaft and for all of my searching I cannot find one. Does anyone have any suggestions?
Thanks

The ideal motor is a Delta/Rockwell 86-920 (1 HP/3phase). Setup an Ebay watchlist. They show up from time to time. The beauty of this motor is that it mounts to the oddball DP600 motor mount. Try a WTB thread at the owwm.org BOYD forum. They are very helpful.

Plan B is a NEMA 56 motor w/shaft bushing but you'll need to make a motor mount adapter. A piece of 5/8" plate aluminum works well. (drilled to mount to the DP's motor mount and drill and tap for the motor. A slightly longer belt will be needed.

I think there are some 3/4" shaft 3 phase motors out there but they are scarce.

P.S. This one might work:

Pardon Our Interruption...

 

[Nmhuntr]

Thanks
That insight helps a lot. I could not figure out model 56 piece. I will likely look for a bushing

 

[Nmhuntr]

Thanks for the suggestions. My next issue is appears will be a motor with a 3” shaft
So my pulley fits it.

 

[Nmhuntr]

The ideal motor is a Delta/Rockwell 86-920 (1 HP/3phase). Setup an Ebay watchlist. They show up from time to time. The beauty of this motor is that it mounts to the oddball DP600 motor mount. Try a WTB thread at the owwm.org BOYD forum. They are very helpful.

Plan B is a NEMA 56 motor w/shaft bushing but you'll need to make a motor mount adapter. A piece of 5/8" plate aluminum works well. (drilled to mount to the DP's motor mount and drill and tap for the motor. A slightly longer belt will be needed.

I think there are some 3/4" shaft 3 phase motors out there but they are scarce.

P.S. This one might work:

Pardon Our Interruption...

Thanks for the suggestions. My next issue it appears will be to ensure it has a 3” long shaft so my pulley will fit it.

 

[Davefr]

Thanks for the suggestions. My next issue it appears will be to ensure it has a 3” long shaft so my pulley will fit it.

If you have the original pulley, 2" is all you need.

 

[Nmhuntr]

If you have the original pulley, 2" is all you need.

It is marked with a DP number but it is 3” deep and the shaft on the aftermarket motor (old but not original) is 3” as well. I should be able to buy any pulley I guess since I will be using a VFD as long as I choose the correct diameter one correct?

 

[micromind]

A 56 frame shaft is 1 - 7/8" long.

If you're using a VFD, a single pulley should work.

A note of caution here, VFDs work best when they are operating at more than 50% speed. Less that that and the torque falls off a bit much more the slower they run.

 

[paulsomlo]

You may find the pdf attachment helpful, regarding motor frame sizes and shaft sizes:

 

[Nmhuntr]

A 56 frame shaft is 1 - 7/8" long.

If you're using a VFD, a single pulley should work.

A note of caution here, VFDs work best when they are operating at more than 50% speed. Less that that and the torque falls off a bit much more the slower they run.

Thanks
One reason I am considering this is to have an easy slow speed option. More research needed

 

[Davefr]

It is marked with a DP number but it is 3” deep and the shaft on the aftermarket motor (old but not original) is 3” as well. I should be able to buy any pulley I guess since I will be using a VFD as long as I choose the correct diameter one correct?

Post an image of the pulley. I've rebuilt 4 DP600s and they all use OEM motors with approx. 2" shafts. The bore of these pulleys is < their height.

No, I'd never use a single grove pulley with a VFD. 90% of the time I use the pulleys on the highest speed and use the VFD to dial down the speed. BUT, sometimes I want maximum torque at very low speeds and adjust the pulleys for lower speed/higher torque and then use the VFD for even lower speeds. (ex: big bits in thick steel)

Having step pulleys AND a VFD gives you maximum flexibility for torque and speed.

 

[Nmhuntr]

Post an image of the pulley. I've rebuilt 4 DP600s and they all use OEM motors with approx. 2" shafts. The bore of these pulleys is < their height.

No, I'd never use a single grove pulley with a VFD. 90% of the time I use the pulleys on the highest speed and use the VFD to dial down the speed. BUT, sometimes I want maximum torque at very low speeds and adjust the pulleys for lower speed/higher torque and then use the VFD for even lower speeds. (ex: big bits in thick steel)

Having step pulleys AND a VFD gives you maximum flexibility for torque and speed.

Thanks a lot for sharing your experience. I will take some photos later and upload them. I like the idea of keeping the multi speed pulleys so I can ensure throat the low speeds should it be needed.

 

[Nmhuntr]

Here are the photos. The shaft is 3” long as is the pulley. Not OEM and hard to read.
Thank you

 

[Davefr]

Here are the photos. The shaft is 3” long as is the pulley. Not OEM and hard to read.
Thank you

That's interesting. The DP600 motor pulleys I've used don't have the shaft hole the full height of the pulley. (maybe 1/2 height). Where is the set screw for the keyway. As long as it can press the keyway on the motor's shaft that's all you need. (The motor's shaft doesn't need to be the full length of the bore.)

That motor in your image is not OEM.

The DP600 motor side step pulley's I'm familiar with look like this. Maybe there were two different styles. Or maybe the pulley in your image is for the spindle end of the DP where the fat part goes on the bottom and needs the bore at that end. Could your pulleys have been mixed up?

 

[Nmhuntr]

That's interesting. The DP600 motor pulleys I've used don't have the shaft hole the full height of the pulley. (maybe 1/2 height). Where is the set screw for the keyway. As long as it can press the keyway on the motor's shaft that's all you need. (The motor's shaft doesn't need to be the full length of the bore.)

That motor in your image is not OEM.

The DP600 motor side step pulley's I'm familiar with look like this. Maybe there were two different styles. Or maybe the pulley in your image is for the spindle end of the DP where the fat part goes on the bottom and needs the bore at that end. Could your pulleys have been mixed up?

The lower set screw is 1.5” up. Looking up part DP645 it appears that this may be a low speed pulley. Correct not OEM motor

 

[Davefr]

The lower set screw is 1.5” up. Looking up part DP645 it appears that this may be a low speed pulley. Correct not OEM motor

That looks correct. You can tighten that set screw on a motor with a 2" shaft. (maybe even the second one). I believe DP644/645 are the slow speed pulley pairs.

 

[Nmhuntr]

That looks correct. You can tighten that set screw on a motor with a 2" shaft. (maybe even the second one). I believe DP644/645 are the slow speed pulley pairs.

Do you have any information on belt setting and RPMs? A lot of these new drill presses have a sticker inside or a badge on the outside to let you know what belt setting for each speed. I guess I can calculate it as well though
Thanks a lot for your help
I really appreciate it

 

[Davefr]

Do you have any information on belt setting and RPMs? A lot of these new drill presses have a sticker inside or a badge on the outside to let you know what belt setting for each speed. I guess I can calculate it as well though
Thanks a lot for your help
I really appreciate it

No I don't. Go over to vintagemachinery.org or owwm.org and you might find the chart

 

[Nmhuntr]

No I don't. Go over to vintagemachinery.org or owwm.org and you might find the chart

Since I will be using a VFD how much of an issue is it to have a motor designed to operate at a lot higher RPM? I am concerned for cooling, and torque. My thought is by limiting it to a slower RPM (1725) that by default the torque would be higher. If I run it at too high an rpm I would need to reduce it via a pulley or I could damage the spindle correct?

 

[micromind]

Since I will be using a VFD how much of an issue is it to have a motor designed to operate at a lot higher RPM? I am concerned for cooling, and torque. My thought is by limiting it to a slower RPM (1725) that by default the torque would be higher. If I run it at too high an rpm I would need to reduce it via a pulley or I could damage the spindle correct?

You'd be better off with a slower motor.

Torque drops off with RPM.

For example, a 1HP 1725RPM motor will produce 3 ft. lbs. of torque. A 1HP 3450 RPM motor will produce 1.5 ft. lbs. of torque but with a VFD it will not produce 3 ft. lbs. at 1725 RPM.

 

[Nmhuntr]

You'd be better off with a slower motor.

Torque drops off with RPM.

For example, a 1HP 1725RPM motor will produce 3 ft. lbs. of torque. A 1HP 3450 RPM motor will produce 1.5 ft. lbs. of torque but with a VFD it will not produce 3 ft. lbs. at 1725 RPM.

Great. That is what I was thinking just wanted an experienced person to confirm my thought
Thanks

 

[lafester]

Where are you located? I bet quite a few of us have spare 3 phase motors.

 

[Nmhuntr]

Where are you located? I bet quite a few of us have spare 3 phase motors.

I am outside Oklahoma City
I think I found one but I am waiting for the details on it